Centrifugal pumps



Jan. 3, 1967 M. PATAY ETAL A v CENTRIFUGAL PUMPS Filed July 26, 1965 United States Patent CENTRIFUGAL PUMPS Miklos Patay, Lajos Patay, and Paul Patay, all of Broadway, Lavington Road, Devizes, England Filed July 26, 1965, Ser. No. 474,872 Claims priority, application Great Britain, Aug. 31, 1964,

9 Claims. (Cl. 103-103) This invention relates to centrifugal pumps, in particular to high specific speed, radial flow, centrifugal pumps.

Radial flow centrifugal pumps, which consist of an impeller arranged for rotation in a casing so as to draw in fluid through the impeller eye parallel to the axis of rotation and expel fluid through outlet passages formed between the impeller vanes normal to the axis of rotation, are generally of relatively low specific speed, in the range of 500 to 4000 rpm. However, a pump designed to deliver relatively large volumes of liquid under relatively low pressure at maximum efiiciency should desirably be of higher specific speed than is normally attainable in a radial flow pump.

According to the present invention a high specific speed, radial flow, centrifugal pump comprises an impeller arranged for rotation Within a casing and having disposed adjacent the periphery thereof a plurality of similar impelling bodies the rear end of each of which is angularly in advance of the forward end of the succeeding impelling body, in which each impelling body is bounded by four faces which extend axially of the impeller and include a short and a long leading face respectively opposite a short and a long trailing face, the short leading face, of each impelling body forming with the long trailing face of the impelling body angularly in advance thereof, an outlet path which, as viewed from the eye of the impeller is convergent and short as measured in the radial direction.

The impelling bodies, suitably, are of uniform axial length. Preferably the total area of the outlet passages at the throats is sensibly equal to the area of the eye of the impeller.

For best results with a pump according to the inven tion, it is desirable that the casing be of the semi-volute type, i.e. that the tongue of the casing be spaced from the periphery of the impeller.

The invention will now be described by way of example with reference to the accompanying, somewhat diagrammatic, drawings in which:

FIGURE 1 is a sectional view of a pump according to the invention taken on the line II of FIGURE 2, and

FIGURE 2 is a sectional plan view on the line II-II of FIGURE 1.

The pump shown in the drawings includes an annular casing 1 having an inlet 3 of 3" diameter, the casing being open about its inner axially extending surface and being of semi-volute shape in plan view, the external radius of which increases from about 3" to about 6". At the part thereof of greatest radius the casing merges with an axially extending outlet branch of 3 diameter. The casing 1 is very little more than 2%" from a top side 7 to a bottom side 9 thereof, and is of substantially uniform depth. On the bottom side 9 of the casing the inner edge of the casing defines the inlet 3 of the pump while the top side 7 of the casing closes the internal area within the annular casing and provides a mounting 11 incorporating bearings 12 and seal 14 for a drive shaft 13 of the pump. The drive shaft 13 extends axially of the casing and carries at its end within the casing an impeller 15 having a disc-like shroud 17 of about 4.75 diameter and A1, thickness, the shroud being disposed parallel to the top side 7 of the casing that carries the ice drive shaft mounting 11. The impeller 15 is secured to the shaft 13 by a dome nut 18.

Four similar, symetrically arranged impelling bodies 19 cast integrally with the shroud 17 are provided on the impeller 15 of the pump and extend from the shroud parallel to the axis of the casing a distance of 2", the axial depth of the impelling bodies being uniform. The total axial depth of the impeller 15 is thus 2%" so that the impeller fits closely within the casing. Each impelling body 19 is disposed between an outer imaginary cylinder 21 of 4.75" diameter, coaxial with the shroud 17, and an inner imaginary cylinder, indicated by broken lines 23, of 3" diameter coaxial with the casing inlet 3. The space within the inner cylinder is the eye 25 of the impeller, and it will be noted that the diameter of the eye is equal to the inlet diameter of the pump. The impelling bodies 19 are slightly tapered towards the inlet.

From its outermost point, i.e. the tip 27, each impelling body 19 extends forwardly in the direction indicated by the arrow 28 in which the impeller 15 is designed to be driven, and inwardly over about 55 of arc, so that the front of one impelling body 19 is spaced from the rear of the preceding impelling body 19 by about '35" of arc. Each impelling body is thus about 2" long, and is about /2" in radial thickness so as to have a long leading face 31 and a long trailing face 33 which are generally parallel and are connected at their ends by two short faces 35 and 37. At its rear, outer end, i.e. adjacent the tip 27, the long leading face 3 1 is almost perpendicular to the radius of the shroud. Further, the long leading face 31 is curved from its rear end gradually inwardly to a sharply inwards curved forward portion 39. The short leading face 35 extends from the forward end of the long leading face inwardly to the eye of the impeller, where it merges into the long trailing face 33 which extends outwardly and rearwardly parallel to the gradually curved portion of the long leading face. The short trailing face 37 which connects the rear ends of the long faces 31 and 33 extends substantially radially.

It will be appreciated that between each pair of successive impelling bodies 19 is an outlet passage 41 through which liquid is accelerated from the eye of the impeller into the casing 1 when the impeller is rotated, and that the short leading face 35 of one body 19 and the long trailing face 33 of the preceding body form a convergent portion, as viewed from the eye 25 of the impeller, of the outlet passage 41, which thus has a throat intermediate and approximately midway between the inner imaginary cylinder 23 and the outer imaginary cylinder 21. It will be observed, too, that the outer cylinder 21 is not appreciably greater in diameter than the inner cylinder 23, the minimum radius of the impelling bodies 19 being 0.63 of the maximum radius. In consequence of this relatively high ratio of minimum to maximum radii, the outlet passages are relatively short in radial extent, and furthermore the impelling bodies can have a small outlet angle,

i.e. a small angle between a tangent to the long leading face 31 at its rear end and a normal to the radius at that end. The outlet angle in the embodiment described is 16.

It should be pointed out that the area of the leading face 31 and 35 which produce positive pressure in the liquid when the impeller is rotated, is substantially equal to the area of the trailing faces 33 and 37, which produce negative pressure or suction when the impeller is rotated so as to draw in liquid from the pump inlet to the eye of the impeller. It is because of the substantial equality of the area of the faces causing positive pressure in the liquid flow with those causing negative pressure or suction in the liquid flow that the pump is referred to as a neutral impeller pump. r

The area of the four throats of the impeller is substantially equal to the area of the eye of the impeller. This relationship is possible because, while the throats are comparatively narrow in a direction from one impelling body to the next, their axial dimension, 2%", is large.

The casing of the pump is as has been stated of semivolute shape. The space between the casing and the impeller increases in the direction of rotation of the impeller from a position marked A at which it is about continuously to a position marked B at the outlet of the casing at which it exceeds somewhat the diameter of the outlet 3.

In use of this pump, the impeller 15 is rotated in the direction 28 by the drive shaft 13, which may be driven by a flexible drive or by a motor coupled directly to the drive shaft. Liquid is sucked in through the inlet 3 to the impeller eye and discharged through the'outlet passages 41 to the casing 1 and thence to the discharge outlet 5. At 2880 r.p.m. the pump will discharge over 456 United States gallons per minute at a pressure head of 38 feet. The specific speed of the pump which is calculated according to the formula MFE 41/H3 where N =specific speed of the impeller in revolutions per minute ==speed of the impeller in revolutions per minute Q=flow of liquid in United States gallons per minute H =head in feet is therefore over 4,000 r.p.m., which is considerably more than usual with a radial flow centrifugal pump. The pump is particularly useful for pumping large volumes of water at relatively low head, as in ditch drainage. Among the features of the pump which co-operate to give this.

high specific speed, are:

the position of the throats 41, which makes part of the outlet passages convergent and so increases the velocity of liquid into the outlet 5, thus reducing the danger of cavitation;

the small radial extent of the outlet passages, which reduces friction and also makes tolerable the increase in radial velocity of liquid through the convergent portions of the passages 41 as well as effecting conversion of velocity energy to pressure energy of liquid in the divergent parts of the outlet passages beyond the throats thereof;

the small outlet angle;

the absence of overlap between adjacent impelling bodies 19, which permits the unobstructed discharge of liquids containing solid matter; and

the relatively large surface area of the impelling bodies, relative to the area of the eye 25, which results from the impelling bodies having four faces.

The various dimensions which have been given for a 3" pump are stated by way of example only, but are broadly indicative of the relative proportions of pumps according to the invention.

If, however, it were required to provide a 3" pump designed to run at higher speed with the same discharge rate and pressure head, the ratio of the radius of the eye of the impeller to the maximum radius of the impelling bodies 19 would be even higher than for the pump de scribed, i.e. the maximum diameter of the impelling body.

is less than the 4.75" described. For a 3" inlet pump, the ratio may lie between 0.4 and 0.75.

In a pump with a 4" inlet of comparable performance, this ratio may be between 0.4 and 0.8, and suitably is near comprising: a casing and an impeller arranged for rotation within said casing, said impeller having a plurality of similar impelling bodies circumferentially spaced from one another about said impeller to form an axially disposed impeller eye, the rear end of each of said impelling bodies being spaced outwardly with respect to the forward end of the next succeeding impelling body, each of said impelling bodies also having four faces extending axially of said impeller, including,,a short, front, leading face and a long, outer, leading face opposite a short, rear, trailing face and a long, inner, trailing face, respectively, said short leading face of each impelling body forming with said long trailing face of the impelling body in advance of it an outlet path between said impelling bodies which is convergent when viewed from said eye of said impeller and short as measured in a radial direction.

2. A pump as claimed in claim 1, wherein the total area of the short and thelong leading faces is substan-. tially equal to the total area of the short and the long trailing faces.

3. A pump as claimed in claim 1, wherein the total area of the minimum cross-sectional areas of the outletpaths between pairs of successive impelling bodies is substantially equal to the area of the eye of the impeller.

4. A pump as claimed in claim 3, wherein the part of the outlet path between each pair of successive impelling bodies which is of minimum cross-sectional area is disposed approximately midway between the circumference of the eye and the outer circumference of said impelling bodies mid-length of the outlet path.

5. A pump as claimed in claim 1, wherein the impeller is disposed in the casing which is of semi-volute form so that the space 'between said impeller and said casing increases progressively in the direction of rotation of the impeller.

6. A pump as claimed in claim 1, wherein the ratio of the diameter of the impeller eye to the maximum diameter of the impeller is greater than 0.4 so that the length i of the outlet path between any pair of successive impelling bodies is short in its radial dimension.

7. A pump as claimed in claim 1, wherein the impeller eye is substantially equal in area to the area of the inlet 1 of the casing and is co-axial with the casing inlet.

8. A high specific, speed radial flow centrifugal pump, comprising: a casing formed with an inlet and an outlet. and an impeller arranged for rotation within said casing,v

said casing having fiat, generally-parallel end walls transverse to the axis of rotation of said impeller, one of which end walls has formed therein said casing-inlet disposed coaxially with said impeller, and side wall means connecting said end walls and generally-circumferentially enclosing said casing, said rotary impeller having a single ring of a plurality of similar impelling bodies adjacent the periphery of said impeller, the rear end of each said impelling body being spaced outwardly with respect to the forward end of the next succeeding impelling body, each said impelling body being bounded by four center of said impeller.

9. A pump as claimed in claim 8 wherein the ratio of the diameter of the impeller eye to the maximum diameter of the impeller is greater than 0.4.

References Cited by the Examiner UNITED STATES PATENTS 1,382,665 6/1921 Meyers 103-115 1,998,694 4/1935 Weinig 103-115 2,606,502 8/1952 Carlson 103-115 6 FOREIGN PATENTS 375,042 5/ 1923 Germany. 574,079 12/ 1945 Great Britain. 472,199 1/ 1952 Italy.

125,058 3/ 1928 Switzerland.

MARK NEWMAN, Primary Examiner.

HENRY F. RADUAZO, Examiner. 

1. A HIGH SPECIFIC SPEED, RADIAL FLOW CENTRIGUGAL PUMP, COMPRISING: A CASING AND AN IMPELLER ARRANGED FOR ROTATION WITHIN SAID CASING, SAID IMPELLER HAVING A PLURALITY OF SIMILAR IMPELLING BODIES CIRCUMFERENTIALLY SPACED FROM ONE ANOTHER ABOUT SAID IMPELLER TO FORM AN AXIALLY DISPOSED IMPELLER EYE, THE REAR END OF EACH OF SAID IMPELLING BODIES BEING SPACED OUTWARDLY WITH RESPECT TO THE FORWARD END OF THE NEXT SUCCEEDING IMPELLING BODY, EACH OF SAID IMPELLING BODIES ALSO HAVING FOUR FACES EXTENDING AXIALLY OF SAID IMPELLER, INCLUDING, A SHORT, FRONT, LEADING FACE AND A LONG, OUTER, LEADING FACE OPPOSITE A SHORT, REAR, TRAILING FACE AND A LONG, INNER, TRAILING FACE, RESPECTIVELY, SAID SHORT LEADING FACE OF EACH IMPELLING BODY FORMING 